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Inelastic mean free path from raw data measured by low-energy electrons time-of-flight spectrometer
Zouhar, Martin ; Radlička, Tomáš ; Oral, Martin ; Konvalina, Ivo
The inelastic mean free path (IMFP) is a key parameter of electron transport in a solid. With\nthe rise of so-called meta-materials, materials of specific shape, such as 2D crystals, or\nmaterials with tailored functionality for next-generation electronic devices, the investigation\nof the IMFP is still topical and of high importance. This is true especially at low energies, landing energy of electrons below 100 eV, that are hard to study using well established\ntechniques of electron spectroscopy.
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Possibilites of a secondary electrons bandpass filter for standard SEM
Mika, Filip ; Pokorná, Zuzana ; Konvalina, Ivo ; Khursheed, A.
Secondary electron filtering in Scanning Electron Microscope (SEM) has been in use for over\na decade. This technique uncovers interesting contrasts in an otherwise ordinary SEM image\nwhich can possibly be used for dopant concentration mapping or for discerning the slight molecular weight differences in apparently homogeneous organic materials. Secondary\nelectron filtering of semiconductor samples seems very promising as it may shed light on the mechanism of SEM image contrast between p-doped and n-doped semiconductors, possibly\nallowing to determine dopant concentration from SEM image alone.
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STEM modes in SEM
Konvalina, Ivo ; Paták, Aleš ; Mikmeková, Eliška ; Mika, Filip ; Müllerová, Ilona
The segmented semiconductor STEM detector in the Magellan 400 FEG SEM microscope\n(https://www.fei.com/) is used to detect transmitted electrons (TEs) and allows observing\nsamples in four imaging modes. Two modes of objective lens, namely high resolution (HR)\nand ultra-high resolution (UHR), differ by their resolution and by the presence or absence of\na magnetic field around the sample. If the beam deceleration (BD) mode is chosen, then\nan electrostatic field around the sample is added and two further microscope modes HR + BD\nand UHR + BD, become available. Trajectories of TEs are studied with regard to their angular\nand energy distribution in each mode in this work.\n
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Very low energy electron transmission spectromicroscopy
Daniel, Benjamin ; Radlička, Tomáš ; Piňos, Jakub ; Mikmeková, Šárka ; Konvalina, Ivo ; Frank, Luděk ; Müllerová, Ilona
For more than 25 years, Scanning Low Energy Electron Microscopy (SLEEM) has been\ndeveloped at the Institute of Scientific Instruments (ISI), with several commercially available SEMs adapted with a cathode lens for SLEEM use, as well as a dedicated self-built UHVSLEEM setup.\nFor a better understanding of contrast formation at low energies, especially at very low energies below 50 eV, where the local density of states plays an important role, more general knowledge about the interaction of (very) low energy electrons with solids is required. This will be achieved using a newly developed ultra-high vacuum (UHV SLEEM) setup which includes several enhancements compared to other available machines. Data processing is presented in, and processed data will be further used and tested with the Monte Carlosimulation package BRUCE, which is being developed by Werner et al. at TU Vienna.
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Scanning transmission microscopy at very low energies
Müllerová, Ilona ; Mikmeková, Eliška ; Konvalina, Ivo ; Frank, Luděk
To operate down to units of eV with a small primary spot size, a cathode lens with a biased specimen was introduced into the SEM. The reflected signal, accelerated secondary and backscattered electrons, is collected by detectors situated above the specimen.\nWhen we insert a detector below the specimen, the transmitted electron signal can also be used for imaging down to zero energy. Fig. 1 also shows an example of the simulated signal trajectories of electrons that impact on the detector of reflected electrons, based on an Yttrium Aluminium Garnet (YAG) crystal, and trajectories of electrons transmitted through the specimen and incident on a semiconductor detector based on the PIN structure.
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Bandpass filter for secondary electrons in SEM - experiments
Mika, Filip ; Konvalina, Ivo ; Krátký, Stanislav ; Müllerová, Ilona
Bandpass energy filtering using a through-the-lens secondary electron (TLD) detector in a field emission gun SEM (FEG-SEM) has been known over a decade. During energy filtering, image contrast is changed and new information about the material can be observed. Our motivation for this study was to compare theoretical calculations with the experimental data\nof the SE bandpass energy filter in Magellan 400 FEG SEM. The TLD detector works as a bandpass energy filter for the special setup of electrode potentials inside the objective lens, with the positive potential on the specimen regulating the energy window.
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Bandpass filter for secondary electrons in SEM - simulations
Konvalina, Ivo ; Mika, Filip ; Krátký, Stanislav ; Müllerová, Ilona
Scanning electron microscope (SEM) is commonly equipped with a through-the-lens secondary electron detector (TLD). The TLD detector in Magellan 400 FEG SEM works as a bandpass filter for the special setup of potentials of electrodes inside the objective lens, the positive potential on the specimen regulates the energy window of the filter. An energy filtered image contains additional information to that of an unfiltered one. The contrast of the filtered image is changed and new information about the topography and the material can be observed.\nTo understand image contrast formation with TLD detector we traced SEs and BSEs through the three-dimensional (3D) model of included 3D distribution of the electrostatic and magnetic fields. The properties of the bandpass filter were simulated for a working distance (WD) in the range of 1 mm to 3 mm and a primary beam energy (EP) from 1 keV to 10 keV.\nThe 3D electrostatic field of the system was calculated by Simion, magnetic field and raytracing were done using EOD program.
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